A new three dose vaccine has recently been developed to prevent
Dengue.

WHO
recommends that the vaccine should be used only in areas where there is 'a high
burden' of the disease.

Before taking the vaccine a blood
test should be done to find out if there is evidence of a prior infection.
This test makes the vaccine safer to use.

Dengue Vaccine – Administer Only in High Burden Regions

The Dengue Vaccine

‘Dengue vaccine – Take only if you are previously infected by the dengue virus.’

The
Dengue fever vaccine, named Dengvaxia has been developed by Sanofi
and was approved in December 2015. It
is a live, recombinant tetravalent (protects
against the four Dengue virus serotypes) vaccine. It has been licensed in six
countries thus far, and many countries are considering how best to administer
the vaccine.

How the Vaccine Acts
within the Body

The
vaccine would act like a natural infection, but without causing the symptoms of
the illness.

For
instance, in persons who have been
previously infected with the Dengue virus, the vaccine acts like a second infection that is mild and asymptomatic,
unlike a naturally occurring second infection that causes serious effects.

On
the other hand, in a person previously uninfected by the virus, the vaccine acts as the first infection, and
a second natural infection occurring at
a later date will be more severe and may need hospitalization.

The Vaccine Trials and
Findings

One
of the chief concerns of scientists developing the vaccine was its safety, and
how to overcome the risk of serious infection that could occur in some
individuals.

Scientists from the
Johns Hopkins Bloomberg School of Public Health, Imperial College London and
the University of Florida have reassessed data from vaccine trials that were
done in 10 countries and included more than 30,000 participants. They also
studied recently published data on their long-term follow up.

Using
the available data, they created
mathematical models that would indicate the efficacy of the vaccine in countries with different rates of transmission of the infection,
namely low, moderate and high.

The
results showed that the vaccine would be effective
in reducing the incidence of infections and hospitalizations by 20 to 30
percent in areas where there was a high transmission rate of Dengue.

On
the other hand, in areas with a lower
transmission rate of the virus, the vaccine significantly increased the
incidence of severe infections and hospitalizations.

Suggested
Recommendations on using the Vaccine

Presently,
the Dengvaxia vaccine is the only one
approved and available to control the spread of Dengue.

"In vaccines you
hope for more than 30 percent success, but it's the only vaccine available
right now to slow dengue," says Isabel Rodriguez-Barraquer, MD, PhD, MHS,
a research associate at the Bloomberg School and one of the study's lead
authors.

Scientists
therefore recommend that the vaccine be used only after carefully

weighing
the risks against the benefits. It should
only be administered when there is enough evidence that it will do more good
than harm.

The
makers of the vaccine too acknowledge the fact that the vaccine is not very
effective in persons not previously infected. The vaccine should not be used in children less than nine years of age since it
is unlikely that they have been previously exposed to the virus.

"We should be careful in considering where and how to use this
vaccine as there is still uncertainty about its impact," says Derek A.T.
Cummings, PhD, a professor of biology at the University of Florida and an
adjunct professor at the Bloomberg School and another of the study's authors.

Based
on these findings, the WHO is
recommending that the vaccine be used only in areas where there is 'a high
burden' of the disease.

"Having a vaccine is a significant step forward for dengue
control," Rodríguez-Barraquer says. "However, this vaccine is a prime
example of having to seriously weigh the risks and benefits."

Something that would help make the decision whether or not to have the
vaccine would be to undergo a blood test
that would reveal evidence of a prior infection.

If a person has evidence of prior infection, it is safe to get
vaccinated; if there is no evidence of previous infection, they should not get
vaccinated.

About Dengue Fever

Dengue is a mosquito borne disease caused by the Dengue
virus, affecting a large global population in tropical countries. It causes high fever with severe headaches, muscle and joint pains, pain
behind the eyeballs and rashes on the limbs and trunk. It is usually
accompanied by a low platelet count
and low white cell count.

Most
persons recover without sequelae,
but a small percentage develop the more
serious Dengue hemorrhagic fever associated with circulatory collapse and
shock referred to as the Dengue Shock
Syndrome. It may be fatal if prompt treatment is not instituted.

Why Secondary Infections are Serious - Virus Tricks the Immune System

There
are four types of Dengue virus that differ slightly in the proteins on their
surface.

Typically,
a first time infection is mild and
the patient recovers completely. However, if a person becomes infected a second
time with a different type of the virus, it leads to a much more serious form
of the disease called Dengue Hemorrhagic Fever that could be fatal in some
cases.

Following
infection with one type of Dengue virus, the immune system reacts normally by
forming antibodies to fight the infection.

When
another infection occurs a second time, the antibodies get confused when faced
with an unfamiliar strain of the virus. Instead of fighting the infection, the
antibodies actually help the virus to attack the immune system, leading to
serious illness.

The
authors of the study hope that the findings and results of their analysis be
borne in mind by policy makers whilst evaluating this as well as other
candidate Dengue vaccines.

Your comments are automatically posted once they are submitted. All comments are however constantly reviewed for spam and irrelevant material (such as product or personal advertisements, email addresses, telephone numbers and website address). Such insertions do not conform to our policy and 'Terms of Use' and are either deleted or edited and republished.Please keep your comments brief and relevant.This section may also have questions seeking help. If you have the information you are welcome to respond, but please ensure that the information so provided is genuine and not misleading.

Disclaimer - All information and content on this site are for information and educational purposes only. The information should not be used for either diagnosis or treatment or both for any health related problem or disease. Always seek the advice of a qualified physician for medical diagnosis and treatment.Full Disclaimer